1. Field of the Invention
This invention in general relates to viewfinder systems for use in photographic cameras but, in particular, to an improved, periscopic viewfinder system of the real image type.
2. Description of the Prior Art
The use of through-the-lens reflex viewfinder arrangements in motion picture cameras is well known. Such arrangements are advantageous because the viewfinder automatically shows the correct field of view irrespective of the focal length of the lens used (especially useful with zoom lenses) and makes visual focusing of the image possible. Commonly, a beamsplitter or small pick-off mirror is positioned in the optical path to direct a percentage of the image forming rays into the viewfinder system which thereafter operates to provide the photographer with a well-defined, usually rectangular, erect image field equal to that covered by the camera lens.
Generally, such viewfinder arrangements extend along one side of the camera from front to back and, as such, usually comprise a periscopic system which classically consists of an objective, an eyelens or eyepiece and one or more field and erector lenses arranged between the objective and eyelens to extend the length of the system or to erect the image or both.
More recently, periscopic viewfinder systems have been disclosed which require fewer optical elements than the classical field/relay lens arrangements. The more recent periscopic arrangements eliminate elements by arranging non-spherical elements so that each element performs in part as both objective lens and field lens.
Examples of the more recent type of periscopic viewfinder systems are shown, e.g., in U.S. Pat. No. 3,583,785 issued to Jack B. Boardman on June 8, 1971 and entitled "Positive Optical System"; U.S. Pat. No. 3,722,979 issued to Nobunao Mikami on Mar. 27, 1973 and entitled "Optical System of the Real Image Type for Finders Having Aspheric Surfaces"; and U.S. Pat. No. 3,792,650 issued to Arthur C. Mueller et al. on Feb. 19, 1974 and entitled "Camera Focus Indicia System."
It is a primary object of the present invention to provide an improved periscopic viewfinder of the more recent type, supra, for use in a photographic camera.
Other objects of the invention in part will be obvious and in part will appear hereinafter. The invention accordingly comprises the apparatus possessing the construction, combination of elements, and arrangement of parts which are exemplified in the following detailed disclosure.